Recent years have seen, especially on the occasion of the playing sports, the frequent use of sunglasses having: a lens of single-lens type made of a plastic resin such as polycarbonate, frames mounted on both side edges of the lens, and temples attached to the respective frames. With some of these sunglasses, a user can selectively change parts such as lenses or frames in order to coordinate their colors and designs suitably for occasions and purposes.
FIG. 12 shows a typical mounting structure of frames and a lens adopted in such sunglasses. Opposite upper side edges of a lens 2 of sunglasses 1 are provided with their respective mounting elements 3 each having its tip portion 3a formed into a hook. Each of a pair of frames 4 is in the form a U-shaped flume with its opening facing downward. A temple 5 is attached to one end in the longitudinal direction of each of the frames 4 and pivotally supported thereby. At the midpoint of each of the frames 4 is provided an engagement piece 6 so that it is held between the opposed inner walls of the corresponding frame 4. Each of the mounting elements 3 is inserted into the frame 4 from the side of the other end in the longitudinal direction of the frame 4, so that the above tip portion 3a comes to mesh with the engagement piece 6.
In the sunglasses 1 with such a mounting structure, although the frames 4 can easily be mounted on or dismounted from the lens 2 (by so-called one-touch operation), if the tip portion 3a is accidentally disengaged from the engagement piece 6, the mounting element 3 of the lens 2 slips down through the downside opening of the frame 4. In short, the frames 4 easily come off the lens 2 by accident, which presents a problem to be solved.